(1) Field of the Invention
The present invention relates to a display device, specifically a liquid crystal display device.
(2) Description of the Related Art
A liquid crystal display device has a TFT substrate, a counter substrate opposing to the TFT substrate, and a liquid crystal layer sandwiched between the TFT substrate and the counter substrate. The TET substrate has plural pixels; each of the pixels has a pixel electrode and a thin film transistor (TFT). Each of the pixels is in an area surrounded by the scan lines and video signal lines. A transmittance of light in each pixel is controlled by liquid crystal molecules; thus, images are formed.
It is necessary to keep the electrical resistance of the video signal lines formed on the TFT substrate low to maintain a wring speed of the video signal data high to each of the pixels. On the other hand, it is difficult to widen the widths of the video signal lines to maintain the light transmittance rate of the pixels. Thus, thickness of the video signal line is made bigger.
On the other hand, if the thickness of the video signal lines is made bigger, reflection of light from the side surface of the video signal line becomes a problem. In other words, light from backlight comes from various directions to the video signal line; if the light from the backlight comes in an oblique direction to the surface of the TFT substrate, the light reflects at a side surface of the video signal line and goes to the display screen; sometimes this is conceived as a line shaped irregularities in brightness in the screen. This phenomenon renders degradation of contrast of a display in total.
The patent document 1 (Japanese patent laid open 2016-148807) discloses to make the width of the common metal wiring, which is superposed with the common electrode to decrease the resistance of the common electrode, wider than the width of the video signal line to stop the light reflected at the side surface of the video signal line (see e.g. FIG. 10).